If you could make one wish for anything in the world -- anything a person could actually grant -- what would you wish for?

Now, imagine if people in your community actually came forward and granted that wish.

How would that extraordinary act of generosity affect you? Would it change your life?

Sure, it would. I say this because I work at Make-A-Wish, where granting wishes is our stock in trade. We grant wishes to children with life-threatening medical conditions to enrich the human experience with hope, strength, and joy. And we see lives changed every day.

We've been granting wishes since 1980, when a group of caring individuals granted the wish of a 7-year-old Phoenix boy with leukemia to be a police officer for a day. They changed little Chris Greicius's life, even though they could not save it.

Convinced they were onto something powerful, they founded Make-A-Wish in his memory. Sunday, April 29 is World Wish Day, the 32nd anniversary of the day Chris got his wish and inspired the creation of Make-A-Wish.

Since that day, we've grown to an organization that last year granted nearly 14,000 wishes to qualified children in the United States, and an additional 8,800 wishes in other countries.

Over the years we've raised an army of volunteers who number more than 30,000 strong, all dedicated to helping the sickest kids among us by teasing out of them what their most heartfelt wish is. Once they have that wish request, they set out to grant the wish. To date, more than 280,000 kids have had their wishes come true.

So what. Why are wishes important? The answer might surprise you. It surprised us.Why choose this cause as our way to help sick children? The act is nice, but is it really necessary?

You bet it is.

Anecdotally, wish kids, their parents, and the community of medical professionals who treat children with life-threatening illnesses continually confirm that the impact of having one's most heartfelt wish come true is substantial and undeniable. But we wanted to dig deeper.

We commissioned a groundbreaking survey among medical professionals, designed to measure wish impact, that was completed in 2011. The responses were much more heartening than even we had anticipated.

Medical professionals reported that children who have their wish granted by Make-A-Wish:

•appear more energetic•are more willing to comply with vital treatment protocol•become more determined in their fight to regain health or quality of life

Those were encouraging indicators of the influence of a wish. But there was a bigger question that has gnawed at us, and many others, for 32 years. And we finally got the answer.

Of those medical professionals -- doctors, nurses, child-life specialists and social workers, all of whom had worked with wish kids -- 89 percent said that the introduction of a wish experience into a young patient's life has the ability to improve physical health.

Not just mental, emotional, or psychological health. Physical health.

To have nearly nine in 10 medical professionals -- a group that typically is overly cautious about attributing cause and effect -- astounded us.

Guess who was not astounded ...The numbers that floored us did not surprise the parents of wish kids we surveyed -- not one bit. They agreed that the wish experience not only helped their sick children -- they said it helped the whole family, and continues to help long after the wish is granted.

The immediate family, after all, serves as young patients' core of support as they fight illness. That core is put to a stress test that can become unbearable as a child descends into the pain of illness and treatment, and the terror of an uncertain future.

Wishes that come true, parents say, create moments where the children regain their identities separate from illness, and take back enough control of their lives to force a return to normalcy for the entire family. And that respite from fighting disease allows all family members to regain their footing, draw together and rejuvenate their efforts to rally around their sick family member.

And what about the wish kids? So many describe the wish experience as a game changer, that pivot point in their journey wherein they regain control of their lives after ceding it to the effects of illness and the demands of fighting it.

Of the many wish kids I have met, perhaps none left such an impression on me as the former wish kid I met four years ago. She had been a teenage girl fighting cancer, which robbed her of her hair, her energy, her self-esteem -- and, she worried -- her future. She wanted to be beautiful again, so she wished to be a fashion model for a day.

We granted that wish, and she changed. She was reminded of her own power, her beauty, and her ability to control her destiny. The wish was a pivot point for her, and boy, did she pivot.

She beat her cancer and went to college. When I caught up with her, she was in medical school.

"After my wish," she told me, "I decided I wanted to be a pediatric oncologist. I'm going to kill the cancer that tried to kill me."

She is one of 280,000 reasons we'll be celebrating World Wish Day on Sunday. I hope you will join us.